HE’S BACK: Carlos Delgado takes a swing as DH for the Carolina Giants last night in Puerto Rico’s winter league. The 37-year-old former Mets slugger had a single in four at-bats in his first game back since May hip surgery. Photo: AP

Jason Bay could officially become a Met today.

The free-agent outfielder, who last week agreed to a four-year deal worth $66 million with the Mets — there is a vesting option for a fifth season — is expected to be in Manhattan today for a full physical, the last step before his deal can become official.

There is some concern on the Mets’ part about Bay’s knees and shoulders, which will be a point of emphasis during today’s examination. The Mets have refused to acknowledge the deal with Bay partly because they fear a public relations fiasco should he fail the physical.

If Bay passes his physical, it’s likely he’ll be introduced to the media tomorrow at Citi Field. It will leave GM Omar Minaya to address holes at catcher and within the starting rotation.

Minaya is still trying to strike a deal with free-agent catcher Bengie Molina and has turned attention in recent days to a starting pitching pool that includes Ben Sheets, Joel Pineiro and Jon Garland.